Harmonic elimination device for voltage transformer and use method thereof
A voltage transformer and harmonic elimination technology, which is applied in the field of voltage transformer harmonic elimination devices, can solve problems such as system failure, burnout voltage transformer, and inability to accurately distinguish power frequency resonance, so as to protect data processing and suppress transients. effect of the process
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Embodiment 1
[0046] Example 1: As attached figure 1 As shown, the voltage transformer resonance elimination device includes a resonance elimination resistor and a control circuit. The resonance elimination resistor is connected across the opening triangle of the voltage transformer. The control circuit is based on the opening triangle voltage U of the voltage transformer. △ Adjust the resistance Rx of the harmonic elimination resistor;
[0047] Set open triangle voltage U of voltage transformer △ There are N sections in the range of (0,100V), set U △i+ Is the maximum voltage value of the i-th section, corresponding to the voltage U of the i-th section △i The harmonic elimination resistance is R i , The calculation formula is:
[0048]
[0049] Among them, N is a natural number; i = 1, 2, ..., N; K is the voltage excitation multiple of the voltage transformer; S is the rated power of the voltage transformer;
[0050] The change range of the open triangle of the voltage transformer is (U △i-1 , ...
Embodiment 2
[0054] Example 2: As attached figure 1 , 2 As shown in 3, a method for using a voltage transformer harmonic elimination device includes the following steps:
[0055] (1) Estimate the voltage of the winding with the highest voltage among the three windings of the open triangle,
[0056] The open triangle voltage of the voltage transformer is the neutral-to-ground voltage U 0 3 times that of U △ = 3U 0 , The voltage vector when the neutral point drifts to point P is The vector sum is versus The vector sum is
[0057] Set the voltage from the neutral point to point P as U 0 , Centered at 0 o'clock U 0 Draw a circle for the radius, U a Is the maximum phase, only when point P is at point Q, Ua is the maximum, and:
[0058] U a =33.33+U 0 =(100+U Δ ) / 3 (2)
[0059] When the neutral point drifts, the maximum phase voltage value estimated by formula (1) shall not be less than the actual maximum phase voltage value. When the neutral point drifts due to unbalanced load, single-phase groundi...
Embodiment 3
[0080] Example 3: Known voltage transformer excitation characteristics Rated voltage factor K = 1.9, open delta winding power per phase S = 50VA, the maximum operating voltage of the system is less than 1.1 times the rated voltage, long-term operation at open delta voltage U △ = 5V, at time T1 U △ Mutation to U △ =70V, at time T2 U △ Back to U △ =100V, at time T3 U △ Back to U △ =5V, automatically track the open triangle voltage to adjust the harmonic elimination resistance.
[0081] Since the maximum operating voltage of the system is less than 1.1 times the rated voltage, according to formula (8), in U △ =Harmonic elimination resistance R at 5V X =2.02 ohm, take R 5 =2.5 ohm; U △ = Harmonic elimination resistance R at 80V X = 55.57 ohm ohm, take R 80 =56 ohm; U △ =Harmonic elimination resistance R at 100V X = 77.19 ohm, take R 100 = 78 ohms.
[0082] First, the long-term operation of the system in U △ =5V, the resistance across the open triangle is R X =R 5 =2.5 ohm; U is measured ...
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